Self-annealing effect of electrolessly deposited copper thin films based on Co(II)–ethylenediamine as a reducing agent

Abstract

A study on the self-annealing of electrolessly deposited copper films on blanket TiN wafers was carried out for different thicknesses. Decrease of 60%–90% in the sheet resistances of 100–260 nm thick copper films was observed after self-annealing. Changes in the copper films’ microstructure were also investigated, including the enhancement of their (111) orientation and grain growth. The pinning of chlorine was found to be influential for self-annealing and Pd activation for electroless deposition played an important role in self-annealing as to microstructural dislocations and defects. In addition, the thinner copper film was more affected by self-annealing. After deposition at room temperature, elevated temperatures accelerated self-annealing and caused decreases in resistivities. The resistivity of a 260 nm thick copper was reduced to 1.7 μΩ cm at 70 °C.